The present invention relates to a solar energy extraction system to produce power in any form desired, and more particularly, to the means of extracting this energy in the most effective and efficient way through a heat exchange process.
For a long time, extracting solar radiative energy for use on a large scale has been sought and and more recently achieved by man. However, to make the process economical and competitive costwise with other means of producing energy, it has to be done on a very large scale with equipment that must operate at peak efficiency, reliably and effectively for a long time. In all systems, other than direct conversion of solar radiation into electricity, the solar rays must be collected and then concentrated on a small surface. This surface absorbs this radiation energy and it can then be used as a source of heat.
This heated surface is cooled by a fluid that keeps this surface at temperatures such that the surface supporting structure can keep its physical integrity for the lifetime of the system. The cooling fluid is heated in the process and, in so doing, extracts the radiation energy which had been absorbed by the heated surfaces exposed to the incident sun rays. A proper balance between the fluid flow and its characteristics, and the heat generated by the surface then maintains the heat exchanger structure at a constant and controlled temperature, but at its peak to maximize the operation efficiency. In most cases, to achieve the highest thermodynamic efficiency for the power generating means that uses the heat transported by the working cooling fluid, the boiler surface and structure must operate at the highest temperature that is compatible with keeping the boiler surface and structure integrity intact and undamaged.
Because it is very difficult to maintain uniform high temperatures over the heated surface of the boiler and because it has to be attached to a cooler supporting structure, one of the major difficulties encountered in building and operating such systems are created by high temperature gradients between one point and another at various locations on that surface, or between that surface and its supporting structure. Such high temperature gradients usually mean high thermal stresses which usually cause structural failures. It is therefore desirable to eliminate the cause of such temperature gradients, but still being able to operate the boiler surface at the highest possible temperatures.